We convert everything to PNG or JPG. The conversion from TGA to PNG is lossless, so you’re getting a smaller file with no change in quality. If your model is available for download or purchase, the original TGAs would still be included.

I’m not sure I see the issue with the alpha / black. Can you elaborate? You do also have some vertex colors that are being multiplied by the Base Color. I don’t know if that’s intentional, but you can disable them if you want.